1. Field of the Invention
The present invention relates generally to a magnetic tape cassette and more specifically to a cassette suited for use with VTR equipment and the like.
2. Description of the Prior Art
Examples of cassettes suitable for use in equipment such as a VTR decks and the like can be found in publications JM-A-51-38749, JM-A-51-41457 and JM-A-62-012103. These devices have included arrangements which are designed to prevent slack from developing in the tape continued therein.
However, these types of arrangements have suffered from the drawbacks that due to the nature of the tensioning arrangement (hereinafter referred to as a tension regulator) which is designed to prevent the development of tape slack, under cetain circumstances is subject to vibration which induces the pads in sliding contact with the tape to resonate and thus deteriorate the tension control of the tape to the point that detrimental effects on the reproduction of the data recorded on the tape occur.
More specifically, FIG. 1 shows a prior art type cassette disclosed in JM-A-62-12103. In this arrangement b denotes the lower half of a cassette case a. This half or shell is formed with two tape apertures c, c' respectively at the forward left and right hand sides thereof. The letter e denotes a magnetic tape which is wound on tape reels d and d' and which is arranged to pass out of the cassette through the previously mentioned tape apertures c, c' and span across the forward face of the device. The lower half b of the cassette is formed with integral tape guides g, g' and f, f' which guide the path of the tape e as it passes from the left reel a, (over guides g and f), out through tape opening c, across the forward end of the cassette, and in through tape aperture c' (over tape guides f' and g') to the right hand reel d'.
The letters h, h' denote resilient sheet like members which define what shall be referred to as tension control pads, which are attached to curved rib-like walls formed in the lower half b of the cassette. These elements form a vital part of a tape tension regulating arrangement. Smooth thin film sheets i and i' are fixed to the respective free ends of the pads h, h'.
As shown, these pads are arranged to slidingly contact the inner surface of the tape e and bias the latter toward and/or into contact with the tape guides g, g'. During non-use, the pads assume the positions illustrated in solid lines, while when the tape is drawn out (shown in phantom) and passed over the reading and recording heads of the VTR deck, a given level of tension is developed which flexes the pads h, h' and induces the latter to move at least partially toward the positions such as illustrated in phantom.
However, with this arrangement, especially as the tape e is wound from reel d to reel d', a large vibration movement particularly in the left hand pad h tends to be produced. Under these conditions, a tension control pin j which forms part of tension control arrangement included in the deck in which the cassette is loaded and which is intended to maintain a fixed level of tension in the tape, tends to be moved in the manner indicated by the arrows in FIG. 1. As a result of the back and forth movement of the tension control pin j, the vibration in pad h tends to be excited to its resonant frequency. The abnormally large movement off pad h due to this resonance tends to exert a highly undesirable influence on the uniformity of the running speed of the tape and cause "jitter" in the image being reproduced.
To overcome this problem, it was thought to increase the rigidity of the pad and thus modify the resonant frequency of the tension regulation arrangements. However, as it is necessary to allow the tape to be readily separated from the guide pins g, g', the degree to which the flexibility of the pads can be modified is limited. Accordingly, a solution to this problem has hitherto not been forthcoming.